Multi-row array RF coil with minimized couplings using birdcage coils

Abstract

Various embodiments of the present disclosure are directed towards a magnetic resonance imaging (MRI) radio frequency (RF) coil array configured to operate in at least one of a transmit mode or a receive mode on a cylindrical former. The MRI RF coil array includes at first row of RF coil elements. Each row of RF coil elements includes at least three RF coil elements that circumferentially surround a cylindrical axis. The MRI RF coil array also includes a first birdcage coil that circumferentially surrounds the first row of RF coil elements. Each RF coil element of the first row is configured to inductively couple to the first birdcage coil and to each other RF coil elements. The first birdcage coil has an impedance configured to negate inductive coupling between the RF coil elements of the first row.

What is claimed is: 
     
       1. A magnetic resonance imaging (MRI) radio frequency (RF) coil array configured to operate in at least one of a transmit (Tx) mode or a receive (Rx) mode on a cylindrical former, the MRI RF coil array comprising:
 a first row of RF coil elements comprising at least three RF coil elements that circumferentially surround an axis; and 
 a first birdcage coil that circumferentially surrounds the first row of RF coil elements, 
 wherein each RF coil element of the first row is configured to inductively couple to the first birdcage coil and to each other RF coil element, and 
 wherein the first birdcage coil has an impedance configured to negate inductive coupling between the RF coil elements of the first row. 
 
     
     
       2. The MRI RF coil array of  claim 1 , wherein the first birdcage coil has a resonant frequency different than a working frequency of the MRI RF coil array. 
     
     
       3. The MRI RF coil array of  claim 1 , wherein each RF coil element of the first row at least partially overlaps with each direct neighboring RF coil element in the first row. 
     
     
       4. The MRI RF coil array of  claim 1 , further comprising:
 a second birdcage coil; 
 a second row of RF coil elements comprising at least three RF coil elements that circumferentially surround the axis; and 
 a third row of RF coil elements comprising at least three RF coil elements that circumferentially surround the axis, 
 wherein the second row is between the first row and the third row along the axis, wherein the first birdcage coil fully surrounds the first row and partially surrounds the second row, wherein the second birdcage coil fully surrounds the third row and partially surrounds the second row, and wherein the first birdcage coil partially overlaps with the second birdcage coil along the axis. 
 
     
     
       5. The MRI RF coil array of  claim 4 , wherein the second row partially overlaps with the first row and the third row along the axis. 
     
     
       6. The MRI RF coil array of  claim 1 , further comprising:
 a second row of RF coil elements comprising at least three RF coil elements that circumferentially surround the axis, 
 wherein the first row is longitudinally offset from the second row along the axis. 
 
     
     
       7. The MRI RF coil array of  claim 6 , wherein the first birdcage coil circumferentially surrounds the first row and the second row, and wherein the impedance is configured to negate inductive coupling between the RF coil elements of the first and second rows. 
     
     
       8. The MRI RF coil array of  claim 6 , wherein each RF coil element of the first row at least partially overlaps with each direct neighboring RF coil element in the second row for decoupling. 
     
     
       9. The MRI RF coil array of  claim 1 , wherein the impedance has an opposite sign as mutual inductance between two RF coil elements in the first row. 
     
     
       10. A magnetic resonance imaging (MRI) radio frequency (RF) coil array comprising:
 a first row of RF coil elements circumferentially arranged around an axis, wherein the first row comprises a first RF coil element and a second RF coil element; and 
 a first birdcage coil circumferentially arranged around the axis, 
 wherein the first row of RF coil elements is between the first birdcage coil and the axis, 
 wherein each RF coil element of the first row is inductively coupled to the first birdcage coil, and 
 wherein a resonant frequency of the first birdcage coil is configured to negate noise between the RF coil elements of the first row. 
 
     
     
       11. The MRI RF coil array of  claim 10 , wherein the first RF coil element has a plurality of mutual inductances respectively with other RF coil elements of the first row, and wherein an impedance of the RF coil element is inversely proportional to an average of the mutual inductances. 
     
     
       12. The MRI RF coil array of  claim 10 , wherein each RF coil element of the first row partially overlaps each direct neighboring RF coil element in the first row. 
     
     
       13. The MRI RF coil array of  claim 10 , wherein the first RF coil element and the second RF coil element comprise individual preamplifiers configured to reduce inductive coupling between the first and second RF coil elements. 
     
     
       14. The MRI RF coil array of  claim 10 , wherein the first birdcage coil comprises:
 a first end ring and a second end ring, wherein the first end ring comprises a capacitor; 
 a plurality of rungs interconnecting the first and second end rings and spaced circumferentially around the axis; and 
 a circuit leg comprising a PIN diode and a reactive element electrically coupled in series, wherein the circuit leg is electrically coupled in parallel with the capacitor, and wherein the reactive element is a capacitor or an inductor, 
 wherein the PIN diode is configured to electrically couple the reactive element in parallel with the capacitor in response to a transmit mode of the MRI RF coil array and to remove the reactive element from in parallel with the capacitor in response to a receive mode of the MRI RF coil array. 
 
     
     
       15. A method comprising:
 providing a magnetic resonance imaging (MRI) radio frequency (RF) coil array comprising: a first row of RF coil elements, wherein the first row comprises at least three RF coil elements circumferentially arranged around an axis; and a first birdcage coil circumferentially arranged around the axis, wherein the first row of RF coil elements is between the first birdcage coil and the axis, and wherein each RF coil element of the first row inductively couples to the first birdcage coil and to each other RF coil element of the first row; and 
 performing an MRI imaging process on a scan target using the MRI RF coil array, wherein the first birdcage coil negates inductive coupling between the RF coil elements. 
 
     
     
       16. The method according to  claim 15 , wherein the performing of the MRI imaging process comprises:
 transmitting RF energy into the scan target with the first birdcage coil, wherein the RF energy is transmitted at a working frequency. 
 
     
     
       17. The method according to  claim 16 , wherein the transmitting comprises changing a resonant frequency of the first birdcage coil from a decoupling frequency to the working frequency, wherein the decoupling and working frequencies are different. 
     
     
       18. The method according to  claim 15 , wherein the performing of the MRI imaging process comprises:
 receiving MRI signals at a working frequency from the scan target using the RF coil elements, wherein the first birdcage coil negates the inductive coupling between the RF coil elements, and has a resonant frequency different than the working frequency, during the receiving. 
 
     
     
       19. The method according to  claim 15 , wherein the at least three RF coil elements comprises a first RF coil element, wherein the first RF coil element has a first mutual inductance with the first birdcage coil, wherein the first RF coil element has a plurality of second mutual inductances respectively with other RF coil elements of the first row, and wherein the first birdcage coil has an impedance that is proportional to a ratio of the first mutual inductance squared to an average of the second mutual inductances to negate the inductive coupling. 
     
     
       20. The method according to  claim 15 , wherein the at least three RF coil elements comprises a first RF coil element and a second RF coil element, wherein the first RF coil element has a first mutual inductance with the first birdcage coil, wherein the first RF coil element has a second mutual inductance with the first RF coil element, and wherein the first and second mutual inductances have opposite signs.